1. Field of the Invention
The present invention relates to a combination weigher which includes weighing hoppers arranged in a circular shape and feeds to a packaging machine or the like products which have been weighed.
2. Description of the Related Art
Typically, products which have been weighed by a combination weigher are fed to, for example, a packaging machine, and are charged into packaging bags or packaging containers. Such a combination weigher which weighs the products is configured to include weighing hoppers arranged in a circular shape or weighing hoppers arranged in a linear shape. In these configurations, for example, below the weighing hoppers, a collecting chute is disposed to gather the products which have been discharged from the weighing hoppers and to discharge the products from a discharge outlet provided at a bottom part thereof to a packaging machine or the like. In the configuration in which the weighing hoppers are arranged in a circular shape, the distances between the weighing hoppers and the discharge outlet of the collecting chute can be made equal. However, in the configuration in which the weighing hoppers are arranged in a linear shape, the distances between the weighing hoppers and the discharge outlet of the collecting chute are different. For this reason, the configuration in which the weighing hoppers are arranged in a circular shape is more preferable than the configuration in which the weighing hoppers are arranged in a linear shape, because it can reduce a difference in a time taken to accomplish the operation in which the products start to be discharged from weighing hoppers selected to form a discharge combination, slide down on the collecting chute, and are discharged from the discharge outlet thereof, and this can attain a high-speed operation. Hereinafter, the combination weigher including the weighing hoppers arranged in a circular shape will be described.
In the conventional combination weigher in which the weighing hoppers are arranged in a circular shape, for example, a dispersion feeder having a substantially conical shape is disposed at an upper part of a center of the combination weigher and a plurality of linear feeders are arranged radially around the dispersion feeder. Below the plurality of linear feeders, a plurality of feeding hoppers are arranged in a circular shape. Below the feeding hoppers, a plurality of weighing hoppers are arranged in a circular shape. Below the plurality of weighing hoppers, a collecting chute is provided to gather the products which have been discharged from the weighing hoppers and to feed the products to, for example, a feed inlet of a packaging machine. For example, a supplying device supplies the products to a center part of the dispersion feeder, which vibrates to transfer the products to the linear feeders. Each linear feeder vibrates to transport the products and feeds them to the feeding hopper. Each feeding hopper temporarily holds the products and feeds the products to the weighing hopper located therebelow. Each weighing hopper weighs the products which have been fed thereto. Combination calculation is performed based on measured values to determine one combination of weighing hoppers in which a total of the measured values falls within an allowable range with respect to a target combination weight and to determine it as a combination (hereinafter referred to as a “discharge combination”) for discharging the products. The weighing hoppers selected to form the discharge combination discharge the products. The discharged products slide down on the collecting chute and are fed into, for example, the feed inlet of the packaging machine.
U.S. Pat. No. 6,066,810 (hereinafter referred to as a “patent document 1”) discloses that, instead of the collecting chute, a belt conveyor is provided to receive products which have been discharged from hoppers selected to form a discharge combination and to gather the products which should be fed to a packaging machine.
Japanese Utility Model Application Registered No. 2528432 (hereinafter referred to as “document 2”) discloses that, instead of the collecting chute, a gutter-shaped conveyor guide member is disposed below weighing hoppers to receive products which have been discharged from weighing hoppers selected to form a discharge combination, a conveyor board movable within the conveyor guide member is provided, and the conveyor board moves to sweep the products from inside of the conveyer guide member to a discharge outlet provided in a predetermined location of the conveyor guide member.
The configuration in which the collecting chute is provided is more preferable than the configuration in which the belt conveyor is provided as disclosed in document 1 or the configuration in which the gutter-shaped conveyor guide member and the conveyor board are provided as disclosed in patent document 2, because a time taken to accomplish the operation in which the products start to be discharged from the hoppers selected to form the discharge combination, are gathered and are discharged to the packaging machine is shorter, achieving a higher-speed operation.
In the above described combination weigher, in the case of, for example, products which have a tendency to stick together, they sometimes stick together and are fed from the linear feeder to the feeding hopper with a large amount at a time. In this case, a large amount of products are fed from the feeding hopper to the weighing hopper. For example, a weighing hopper which is fed with the products with an amount that is larger than an upper limit value of an allowable range with respect to the target combination weight, is not selected for the discharge combination. In a case where favorable combination weighing accuracy is attained by setting the number of weighing hoppers selected to form the discharge combination to four in average, the operation is set so that a target feed amount for the weighing hopper is ¼ or substantially ¼ of the target combination weight. It is difficult to select for the discharge combination the weighing hopper which is fed with the products whose amount is significantly larger than the target feed amount, for example, twice as large as the target feed amount. This is because, if such a weighing hopper participates in a combination within a predetermined weight range, then the number of other weighing hoppers which can participate in the combination becomes smaller.
In a case where a package containing a predetermined number of products is manufactured, a combination of weighing hoppers in which a total weight of the products falls within the allowable range with respect to the target combination weight and a total number of the products is a predetermined number is determined as the discharge combination. In this case, when the products are fed with a large amount at a time from the linear feeder to the feeding hopper and the products whose number is larger than the predetermined number are fed from the feeding hopper to the weighing hopper as described above, this weighing hopper is not selected for the discharge combination. In a case where favorable combination weighing accuracy is attained by setting the number of weighing hoppers selected to form the discharge combination to four in average and a package containing a smaller number, for example, seven pieces of products is manufactured, each weighing hopper must be configured to be fed with one to two pieces of products. For example, if a weighing hopper is fed with eight pieces of products, then the weighing hopper is not selected for the discharge combination.
If the weighing hopper which is fed with the products with an excess amount (hereinafter referred to as an “excess product weighing hopper”) as described above increases in number, then it becomes impossible to determine the discharge combination. Accordingly, to eliminate the excess product weighing hopper, the products must be discharged from the excess product weighing hopper. In an example of a method for achieving this, a combination weigher is operated in such a manner that the excess product weighing hopper is displayed on a screen of a display device equipped in the combination weigher and an operator removes the products from the excess product weighing hopper. To this end, manual intervention is required to remove the products from the excess product weighing hopper and a productive capacity is reduced.
In another example of the method, for example, a collecting hopper capable of discharging the products to be weighed in two directions is provided at a discharge outlet of the collecting chute, and a first chute is provided to route to the feed inlet of the packaging machine the products which have been discharged in one direction from the collecting hopper, while a second chute is provided to route to a specified discharge area the products which have been discharged in the other direction from the collecting hopper. In this case, the products which have been discharged from the weighing hopper selected to form the discharge combination are held in the collecting hopper and then are discharged to the first chute. On the other hand, the products which have been discharged from the excess product weighing hopper are held in the collecting hopper and then are discharged to the second chute. When the products are discharged from the excess product weighing hopper, the weighing hopper selected to form the discharge combination must stop discharging for a moment, causing a reduced productive capacity.